Darker than Black

In a Holy Grail War, Mages (Masters) and their Heroic Spirits (Servants) fight for the control of the Holy Grail—an omnipotent wish-granting device said to fulfill any desire. Years have passed since the end of the Fifth Holy Grail War in Japan. Now, signs portend the emergence of a new Holy Grail in the western American city of Snowfield. Sure enough, Masters and Servants begin to gather... A missing Servant class... Impossible Servant summonings... A nation shrouded in secrecy... And a city created as a battleground. In the face of such irregularities, the Holy Grail War is twisted and driven into the depth of madness. Let the curtain rise on a masquerade of humans and heroes, made to dance upon the stage of a false Holy Grail.

The Medicine Seller is a deadly and mysterious master of the occult who travels across feudal Japan in search of malevolent spirits called mononoke to slay. When he locates one of these spirits, he cannot simply kill it; he must first learn its Form, its Truth, and its Reason in order to wield the mighty Exorcism Sword and fight against it. He must begin his strange exorcisms with intense psychological analysis and careful investigative work—an extremely dangerous step, as he must first confront and learn about the mononoke before he even has the means to defeat it.

Spurred by the flame raging in his heart, the Black Swordsman Guts continues his seemingly endless quest for revenge. Standing in his path are heinous outlaws, delusional evil spirits, and a devout child of god. Even as it chips away at his life, Guts continues to fight his enemies, who wield repulsive and inhumane power, with nary but his body and sword—his strength as a human.

A supernatural system allows people to take revenge by having other people sent to Hell via the services of a mysterious entity and her assistants who implement this system. Revenge, injustice, hatred, and the nature of human emotions are common themes throughout the series.